Preparation method of Sn-Er-beta molecular sieve and application thereof

Abstract

The application discloses a preparation method and application of Sn-Er-Beta molecular sieve, which comprises two parts of catalyst preparation and catalytic reaction. The catalyst preparation process is composed of three steps of molecular sieve dealumination, Sn introduction in a water bath mode and Er introduction by solid-state ion exchange. The catalytic reaction is mixing of saccharides, the catalyst and water, heating to 180 DEG C-220 DEG C without inert gas protection for 1h-4h to obtain a target product lactic acid. Under certain reaction conditions, the Sn-Er-Beta catalyst can obtain a lactic acid yield of 71.2% in catalyzing glucose, and a lactic acid yield of more than 90% in catalyzing hydroxypropanone and acetylaldehyde. The molecular sieve catalyst of the application is simple to prepare and has high selectivity in catalytic conversion of saccharides into lactic acid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and relates to the preparation of a molecular sieve, in particular to a preparation method of Sn-Er-Beta molecular sieve and application of Sn-Er-Beta molecular sieve prepared by the method to catalytic conversion of sugars to lactic acid. BACKGROUND

[0002] The global environmental pollution problem caused by overexploitation of fossil fuel resources and carbon emissions is becoming increasingly serious. Reducing energy demand, finding environmentally friendly alternative energy sources, and developing sustainable production processes are all ways for people to transition to green and low-carbon production and life. Biomass is a green and sustainable resource that is fixed by photosynthesis of green plants from carbon dioxide in the atmosphere and stored in various organic forms. At present, there are many types of biomass resources and a huge amount of available biomass. According to biologists, more than one hundred billion tons of organic matter are synthesized by photosynthesis in nature every year, far exceeding the total energy demand of the world, so the market for the practical use of biomass resources is very broad. However, the actual utilization rate is very low.

[0003] As the main component of biomass resources, how to efficiently utilize sugars has always been the focus of industrial application. Converting sugars into other chemicals not only reduces dependence on petroleum resources, but also reduces pollution during the exploitation and utilization of fossil resources. Lactic acid is a high-value organic compound with a wide range of applications, such as preservative, pH regulator, and cleaning agent.

[0004] Lactic acid is mainly produced by biological fermentation and chemical synthesis. However, the biological fermentation process has a long cycle, high downstream separation and purification and processing costs, and the conversion rate of lactic acid obtained by conventional chemical synthesis process is low. Therefore, it is of great industrial value to develop an economical and practical lactic acid preparation process.

[0005] Current chemical catalytic methods mainly rely on catalysts to achieve high yield of lactic acid. Although there are many types of existing catalysts, there are few green and environmentally friendly catalysts that can be used in industrial application to produce lactic acid due to simple preparation process, short preparation period, no need for dangerous chemicals, and low recycling performance. Therefore, developing an efficient method for catalyzing sugar to produce lactic acid has always been a research hotspot in the utilization of biomass resources.

[0006] Zeolite molecular sieve has high application value due to its good thermal stability, hydrophobicity and structural selectivity. However, the existing molecular sieve still has the disadvantages of long preparation period, complex preparation process, many by-products, and low recycling performance, which does not meet the concept of green and low-carbon production process and does not have the basic conditions for industrial application. Therefore, it is of great significance to develop a method for catalyzing sugar to produce lactic acid with short preparation period and green environmental protection. SUMMARY

[0007] In order to solve the above problems, the present application firstly provides a preparation method of Sn-Er-Beta molecular sieve, the catalyst in the present application uses dibutyl tin diacetate as tin source and is introduced into the molecular sieve through water bath method, uses erbium oxide as erbium source and is introduced into the molecular sieve through solid ion exchange method, and the preparation method has the advantages of simple preparation condition, short preparation period, high lactic acid yield and good recycling performance.

[0008] The present application further provides the application of the Sn-Er-Beta molecular sieve prepared by the above method in catalytic conversion of sugar to obtain lactic acid.

[0009] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0010] In the first aspect, the present application provides a preparation method of Sn-Er-Beta molecular sieve, and the preparation method comprises the following steps:

[0011] 1) mixing Beta molecular sieve with concentrated nitric acid, performing aluminum removal treatment under certain temperature conditions through magnetic stirring, taking out the mixture, performing centrifugation and pure water washing until the pH of the washing liquid is neutral, and drying to obtain aluminum-removed Beta molecular sieve;

[0012] 2) mixing the aluminum-removed Beta molecular sieve obtained in step 1) with water, ethanol and 25% tetraethylammonium hydroxide aqueous solution, adding dibutyl tin diacetate dropwise, performing magnetic stirring reaction under the condition of 40℃-60℃, taking out the mixture, performing centrifugation and pure water washing until the pH of the washing liquid is neutral, and drying to obtain Sn-Beta molecular sieve;

[0013] 3) mixing the Sn-Beta molecular sieve obtained in step 2) with erbium oxide, grinding, and calcining under the condition of argon atmosphere to obtain Sn-Er-Beta molecular sieve.

[0014] As a preferred scheme of the present application, in step 1), the temperature of magnetic stirring is 80℃, and the rotating speed is 200rpm; 20mL of concentrated nitric acid is added per 1g of Beta molecular sieve; and the drying temperature is 120℃, and the drying time is 8h-10h.

[0015] As a preferred scheme of the present application, in step 2), the volume ratio of water, ethanol and 25% tetraethylammonium hydroxide aqueous solution is 1:1:1, the total volume of water, ethanol and 25% tetraethylammonium hydroxide aqueous solution added per 1g of Beta molecular sieve is 15mL-20mL; the amount of dibutyl tin diacetate added per 1g of Beta molecular sieve is 1mmol-1.5mmol in terms of Sn, the reaction temperature is 40℃-60℃, and the reaction time is 6h; and the drying temperature is 120℃, and the drying time is 8h-10h.

[0016] As a preferred scheme of the present application, in step 3), the mixing ratio of Sn-Beta molecular sieve and erbium oxide is 1 mmol-1.5 mmol of erbium oxide per 1 g of Sn-Beta molecular sieve, the calcination temperature is 450-550°C, and the calcination time is 6-8 hours.

[0017] As a preferred scheme of the present application, the atomic ratio of Si / Al in the Beta molecular sieve is 30-40.

[0018] In a second aspect, the present application provides the use of the Sn-Er-Beta molecular sieve prepared by the above method in catalytic conversion of sugar to lactic acid.

[0019] As a preferred scheme of the present application, the method for catalytic conversion of sugar using the Sn-Er-Beta molecular sieve includes: adding sugar, the Sn-Er-Beta molecular sieve prepared by the above method, and pure water into a reaction container, placing the reaction container in a stainless steel reaction kettle and fixing it on a rotary oven for heating to perform a catalytic reaction, taking out the reaction mixture in the kettle after the reaction is completed, centrifuging using a centrifuge, diluting and filtering the supernatant, and drying the solid substance after washing and centrifuging with pure water, which can be used as a catalyst again after activation; the catalytic reaction does not require inert gas protection.

[0020] As a preferred scheme of the present application, the sugar includes any one of glucose, fructose, hydroxypropanone, and methylglyoxal; and the catalytic reaction is performed by adding 0.1-1 mmol of sugar substrate and 0.5-1.5 mL of pure water per 10 mg of Sn-Er-Beta molecular sieve.

[0021] As a preferred scheme of the present application, in the catalytic reaction, the rotation rate of the rotary oven is 10-30 r / min, the heating temperature is 180-220°C, and the reaction time is 1-4 hours; and the centrifugation rate is 8000-11000 r / min, and the centrifugation time is 4-6 minutes, so as to achieve the best solid-liquid separation effect.

[0022] As a preferred scheme of the present application, the activation process is calcination of the solid substance in an argon atmosphere at 450-550°C for 6-8 hours.

[0023] In the present application, the dilution multiple of the reaction mixture is 100-300 times to meet the product standard curve range, and a water phase filter membrane with a pore size of 0.45 μm or below is used for filtration.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The catalyst in the application uses dibutyl tin diacetate as a tin source to introduce the molecular sieve by a water bath method, and uses erbium oxide as an erbium source to introduce the molecular sieve by a solid-state ion exchange method, and has the advantages of short preparation period, high lactic acid yield, and good recycling performance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a preparation method of Sn-Er-Beta molecular sieve and a process schematic diagram of catalyzing sugar to produce lactic acid.

[0027] Figure 2 is a TEM transmission electron microscope element scanning schematic diagram of Sn-Er-Beta molecular sieve. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the application is further described below in combination with specific embodiments, but the following embodiments are only preferred embodiments of the application, not all. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application. In the following examples, the experimental methods are conventional methods, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0029] Referring to Figure 1 The application first provides a preparation method of Sn-Er-Beta molecular sieve. The catalyst in the application uses dibutyl tin diacetate as a tin source to introduce the molecular sieve by a water bath method, and uses erbium oxide as an erbium source to introduce the molecular sieve by a solid-state ion exchange method, and has the advantages of simple preparation condition, short preparation period, high lactic acid yield, and good recycling performance.

[0030] Then, the Sn-Er-Beta molecular sieve prepared by the above method is used to catalyze sugar to obtain lactic acid, and has the advantages of high lactic acid yield and good recycling performance.

[0031] Example 1

[0032] The embodiment provides a preparation method of Sn-Er-Beta molecular sieve and a method for catalyzing sugar to obtain lactic acid by using the Sn-Er-Beta molecular sieve, and the method comprises the following steps.

[0033] 1) Catalyst preparation: Beta molecular sieve with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial grade Beta molecular sieve), and subjected to magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was removed, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain dealuminated Beta molecular sieve. 1 g of the dealuminated Beta molecular sieve was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% aqueous tetraethylammonium hydroxide solution, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to magnetic stirring reaction at 60°C for 6 h. The mixture was removed, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain Sn-Beta molecular sieve. 1 g of the Sn-Beta molecular sieve was mixed with 1 mmol of erbium oxide, and then ground for 20 min. The mixture was calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta molecular sieve.

[0034] 2) Catalytic conversion reaction: 225 mg of glucose, 180 mg of Sn-Er-Beta molecular sieve, and 10 mL of pure water were added to a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary oven was rotated at a speed of 20 r / min, and the reaction time was 2 h.

[0035] Referring to Figure 2 As shown in the TEM transmission electron microscope element scanning schematic diagram of the Sn-Er-Beta molecular sieve, it can be seen that the Al element in the molecular sieve is basically removed in the dealumination process, and the introduced Sn species and Er species are uniformly dispersed in the molecular sieve.

[0036] Referring to Table 1, the lactate yield of the Sn-Er-Beta molecular sieve catalyzing sugar is shown in Table 1. The lactate yield of the obtained product catalyzing glucose is 71.2%.

[0037] Example 2

[0038] The present embodiment provides a preparation method of Sn-Er-Beta molecular sieve and a method for catalyzing sugar conversion to obtain lactic acid using the same, which comprises:

[0039] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial Beta zeolite), and was subjected to magnetic stirring at 80°C for 20 h to remove aluminum. The mixture was removed, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain the aluminum-removed Beta zeolite. 3 g of the aluminum-removed Beta zeolite was mixed with 15 mL of water, 15 mL of ethanol, and 15 mL of 25% aqueous solution of tetraethylammonium hydroxide, and then 5 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to magnetic stirring at 60°C for 6 h, and then was removed, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain Sn-Beta zeolite. 3 g of the Sn-Beta zeolite was mixed with 5 mmol of erbium oxide, and was ground for 20 min. The mixture was calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite.

[0040] 2) Catalytic conversion reaction: 225 mg of glucose, 200 mg of Sn-Er-Beta zeolite, and 10 mL of pure water were added into a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was increased to 200°C to start timing. The rotary speed of the rotary oven was 20 r / min, and the reaction time was 2 h.

[0041] The yield of lactic acid catalyzed by the Sn-Er-Beta zeolite was 65.4%, which was lower than that in Example 1. The more dibutyltin diacetate and erbium oxide were added, the more the performance of the catalyst could not be obviously enhanced.

[0042] Example 3

[0043] The present example provides a method for preparing Sn-Er-Beta zeolite and a method for catalyzing conversion of sugars to obtain lactic acid using the same, which comprises:

[0044] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial Beta zeolite), and was subjected to a magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was removed, centrifuged, and washed with pure water until the pH of the washing liquid showed neutrality. Then, the mixture was dried at 120°C for 8 h to obtain dealuminated Beta zeolite. 3 g of the dealuminated Beta zeolite was mixed with 20 mL of water, 20 mL of ethanol, and 5 mL of 25% aqueous solution of tetraethylammonium hydroxide. Then, 3 mmol of Sn calculated as dibutyltin diacetate was added dropwise, and the mixture was subjected to a magnetic stirring reaction at 60°C for 6 h. The mixture was removed, centrifuged, and washed with pure water until the pH of the washing liquid showed neutrality. Then, the mixture was dried at 120°C for 8 h to obtain Sn-Beta zeolite. 3 g of the Sn-Beta zeolite was mixed with 3 mmol of Er calculated as erbium oxide, and was ground for 20 min. Then, the mixture was calcined at 550°C in an argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite.

[0045] 2) Catalytic conversion reaction: 225 mg of glucose, 180 mg of Sn-Er-Beta zeolite, and 10 mL of pure water were added to a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary speed of the rotary oven was 20 r / min, and the reaction time was 2 h.

[0046] The yield of lactic acid catalyzed by the Sn-Er-Beta zeolite from sugar was 56.9%, which was lower than that in Example 1. The use of too little tetraethylammonium hydroxide can reduce the performance of the catalyst.

[0047] Example 4

[0048] This example provides a method for preparing Sn-Er-Beta zeolite and a method for catalyzing the conversion of sugar to lactic acid using the same, which comprises:

[0049] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL concentrated nitric acid was added per 1 g of commercial Beta zeolite), and was subjected to a magnetic stirring dealumination treatment at 80°C for 10 h. The mixture was removed, centrifuged, and washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain dealuminated Beta zeolite. 1 g of the dealuminated Beta zeolite was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% tetraethylammonium hydroxide aqueous solution, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to a magnetic stirring reaction at 60°C for 6 h. The mixture was removed, centrifuged, and washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain Sn-Beta zeolite. 1 g of the Sn-Beta zeolite was mixed with 1 mmol of erbium oxide, and was ground for 20 min. The mixture was calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite.

[0050] 2) Catalytic conversion reaction: 75 mg of glucose, 60 mg of Sn-Er-Beta zeolite, and 5 mL of pure water were added to a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary speed of the rotary oven was 20 r / min, and the reaction time was 2 h.

[0051] The Sn-Er-Beta zeolite catalyzed the conversion of sugars to lactic acid with a yield of 61.7%, which was lower than that in Example 1. Incomplete dealumination process can lead to a decrease in the performance of the catalyst.

[0052] Example 5

[0053] This example provides a method for preparing Sn-Er-Beta zeolite and a method for catalyzing the conversion of sugars to lactic acid using the same, which comprises:

[0054] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial Beta zeolite), and subjected to magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain dealuminated Beta zeolite. 1 g of the dealuminated Beta zeolite was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% aqueous tetraethylammonium hydroxide solution, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to magnetic stirring reaction at 60°C for 6 h. The mixture was taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain Sn-Beta zeolite. 1 g of the Sn-Beta zeolite was mixed with 1 mmol of erbium oxide, and then ground for 20 min. The mixture was calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite.

[0055] 2) Catalytic conversion reaction: 225 mg of fructose, 180 mg of Sn-Er-Beta zeolite, and 10 mL of pure water were added to a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary oven was rotated at a speed of 20 r / min, and the reaction time was 2 h.

[0056] The Sn-Er-Beta zeolite catalyzed the conversion of sugars to lactic acid, and the lactic acid yield was 71.8%, which was comparable to the lactic acid yield obtained by catalyzing glucose.

[0057] Example 6

[0058] The present embodiment provides a method for preparing Sn-Er-Beta zeolite and a method for catalyzing the conversion of sugars to lactic acid using the same, which comprises:

[0059] 1) Catalyst preparation: Beta molecular sieve with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial grade Beta molecular sieve), and was subjected to magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain dealuminated Beta molecular sieve. 1 g of the dealuminated Beta molecular sieve was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% aqueous solution of tetraethylammonium hydroxide, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to magnetic stirring reaction at 60°C for 6 h. The mixture was taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then was dried at 120°C for 8 h to obtain Sn-Beta molecular sieve. 1 g of the Sn-Beta molecular sieve was mixed with 1 mmol of erbium oxide, and was ground for 20 min. The mixture was calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta molecular sieve.

[0060] 2) Catalytic conversion reaction: 225 mg of 1,3-dihydroxyacetone, 180 mg of Sn-Er-Beta molecular sieve, and 10 mL of pure water were added into a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary speed of the rotary oven was 20 r / min, and the reaction time was 2 h.

[0061] The lactic acid yield of the Sn-Er-Beta molecular sieve catalyzed sugar is shown in Table 1. The lactic acid yield in the product obtained by catalyzing 1,3-dihydroxyacetone was 96.6%, indicating that the Sn-Er-Beta molecular sieve catalyst has good catalytic effect on the dehydration reaction of dihydroxyacetone.

[0062] Example 7

[0063] The present embodiment provides a preparation method of Sn-Er-Beta molecular sieve and a method for obtaining lactic acid by catalyzing sugar conversion using the same, which comprises:

[0064] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial Beta zeolite), and subjected to magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was then taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain dealuminated Beta zeolite. 1 g of the dealuminated Beta zeolite was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% aqueous tetraethylammonium hydroxide solution, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to magnetic stirring reaction at 60°C for 6 h. The mixture was then taken out, centrifuged, washed with pure water until the washing liquid showed neutral pH, and then dried at 120°C for 8 h to obtain Sn-Beta zeolite. 1 g of the Sn-Beta zeolite was mixed with 1 mmol of erbium oxide, and then ground for 20 min. The mixture was then calcined at 550°C under argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite.

[0065] 2) Catalytic conversion reaction: 180 mg of methylglyoxal, 180 mg of Sn-Er-Beta zeolite, and 10 mL of pure water were added into a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary speed of the rotary oven was 20 r / min, and the reaction time was 2 h.

[0066] The Sn-Er-Beta zeolite catalyzed the production of lactic acid from sugars, and the lactic acid yield was 94.2% in the product obtained by catalyzing methylglyoxal, indicating that the Sn-Er-Beta zeolite catalyst had good catalytic effect on the isomerization reaction of methylglyoxal.

[0067] Table 1. Sn-Er-Beta zeolite catalyzed lactic acid yield from sugars

[0068]

[0069] Example 8

[0070] The present example provides a method for preparing Sn-Er-Beta zeolite and a method for catalyzing the conversion of sugars to lactic acid using the same, which comprises:

[0071] 1) Catalyst preparation: Beta zeolite with Si / Al ratio of 35 was mixed with concentrated nitric acid (20 mL of concentrated nitric acid was added per 1 g of commercial Beta zeolite), and subjected to a magnetic stirring dealumination treatment at 80°C for 20 h. The mixture was then removed, centrifuged, washed with pure water until the pH of the washing liquid showed neutrality, and then dried at 120°C for 8 h to obtain dealuminated Beta zeolite. 1 g of the dealuminated Beta zeolite was mixed with 5 mL of water, 5 mL of ethanol, and 5 mL of 25% tetraethylammonium hydroxide aqueous solution, and then 1 mmol of dibutyltin diacetate was added dropwise. The mixture was subjected to a magnetic stirring reaction at 60°C for 6 h. The mixture was then removed, centrifuged, washed with pure water until the pH of the washing liquid showed neutrality, and then dried at 120°C for 8 h to obtain Sn-Beta zeolite. 1 g of the Sn-Beta zeolite was mixed with 1 mmol of erbium oxide, ground for 20 min, and then calcined at 550°C in an argon atmosphere for 6 h to obtain Sn-Er-Beta zeolite;

[0072] 2) Catalytic conversion reaction: 225 mg of glucose, 180 mg of Sn-Er-Beta zeolite, and 10 mL of pure water were added to a reaction kettle. The reaction kettle was placed in a rotary oven, and the temperature in the oven was allowed to rise to 200°C to start timing. The rotary oven was rotated at a speed of 20 r / min, and the reaction time was 2 h. The obtained product was centrifuged and washed, and the obtained catalyst was activated and used as a catalyst again;

[0073] 3) Recycling experiment: the solid residue after the reaction in step 2) was washed with pure water and centrifuged 3 times, and then dried at 120°C for 8 h and calcined at 550°C in an argon atmosphere for 6 h to obtain recycled Sn-Er-Beta zeolite. The recycling experiment in step 3) was repeated 5 times after the catalytic reaction in step 2);

[0074] The catalytic performance of the Sn-Er-Beta zeolite recycled 1, 2, 3, 4, and 5 times decreased from the second recycling. The lactic acid yield from the catalytic conversion of glucose was 67%, and the catalytic performance decreased slightly during the recycling for 3-5 times, and the lactic acid yield from the catalytic conversion of glucose was maintained at about 45%, indicating that the Sn-Er-Beta zeolite had good recycling performance.

[0075] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form or in essence. It should be noted that those skilled in the art can make some improvements and supplements without departing from the method of the present application, and these improvements and supplements should also be considered as the protection scope of the present application. For those skilled in the art, some slight changes, modifications and equivalent changes made by using the disclosed technical content without departing from the spirit and scope of the present application are equivalent embodiments of the present application; meanwhile, any equivalent changes, modifications and evolution made according to the essential technology of the present application to the above embodiments are still within the scope of the technical solutions of the present application.

Claims

1. A method for preparing Sn-Er-Beta molecular sieve, characterized in that, The preparation method comprises the following steps: 1) mixing the Beta molecular sieve with concentrated nitric acid, performing a magnetic stirring dealumination treatment under certain temperature conditions, taking out the mixture, and then performing centrifugation and pure water washing until the washing liquid is neutral in pH, and drying to obtain the dealuminated Beta molecular sieve; 2) mixing the dealuminated Beta molecular sieve obtained in step 1) with water, ethanol and 25% tetraethylammonium hydroxide aqueous solution, adding dropwise dibutyltin diacetate, and performing a magnetic stirring reaction under the condition of 40-60 DEG C, taking out the mixture, performing centrifugation and pure water washing until the washing liquid is neutral in pH, and drying to obtain the Sn-Beta molecular sieve; 3) mixing the Sn-Beta molecular sieve obtained in step 2) with erbium oxide, grinding, and calcining under an argon atmosphere to obtain the Sn-Er-Beta molecular sieve; In step 2), the volume ratio of water, ethanol and 25% tetraethylammonium hydroxide aqueous solution is 1:1:1, the total volume of water, ethanol and 25% tetraethylammonium hydroxide aqueous solution added per 1g of Beta molecular sieve is 15-20mL, the amount of dibutyltin diacetate added per 1g of Beta molecular sieve is 1-1.5mmol of Sn, the reaction temperature is 40-60 DEG C, and the reaction time is 6h; the drying temperature is 120 DEG C, and the drying time is 8-10h; In step 3), the mixing ratio of the Sn-Beta molecular sieve and the erbium oxide is that the amount of erbium oxide added per 1g of Sn-Beta molecular sieve is 1-1.5mmol of Er, the calcining temperature is 450-550 DEG C, and the calcining time is 6-8h. The Si / Al atomic ratio of the Beta molecular sieve is 30-40. 2.The method for preparing Sn-Er-Beta molecular sieve according to claim 1, characterized in that, In step 1), the magnetic stirring temperature is 80 DEG C, the rotating speed is 200rpm, 20mL of concentrated nitric acid is added per 1g of Beta molecular sieve, the drying temperature is 120 DEG C, and the drying time is 8-10h.

3. Use of a Sn-Er-Beta zeolite prepared according to the process of any one of claims 1 to 2, characterized in that, The application of the Sn-Er-Beta molecular sieve in catalyzing the conversion of sugar and methylglyoxal to obtain lactic acid.

4. The use of the Sn-Er-Beta molecular sieve according to claim 3, characterized in that The method for catalyzing the conversion of sugar by the Sn-Er-Beta molecular sieve comprises the following steps: adding sugar, the Sn-Er-Beta molecular sieve prepared by the method in any one of claims 1-2 and pure water into a reaction container, placing the reaction container into a stainless steel reaction kettle and fixing the reaction kettle on a rotary oven to perform a catalytic reaction, taking out the reaction mixture in the kettle after the reaction is completed, performing centrifugation by using a centrifuge, diluting and filtering the upper clear liquid, and then performing high performance liquid chromatography analysis and testing, washing, centrifuging and drying the lower solid substance for multiple times, and activating the lower solid substance to be used as a catalyst again.

5. The use of the Sn-Er-Beta molecular sieve according to claim 4, characterized in that The sugar comprises any one of glucose, fructose and hydroxypropanone; and the catalytic reaction is performed by adding 0.1-1mmol of sugar substrate and 0.5-1.5mL of pure water per 10mg of Sn-Er-Beta molecular sieve.

6. The use of the Sn-Er-Beta molecular sieve according to claim 4, characterized in that In the catalytic reaction, the rotation rate of the rotation oven is 10r / min-30r / min, the heating temperature is 180℃-220℃, and the reaction time is 1h-4h; the centrifugal rate is 8000r / min-11000r / min, and the centrifugal time is 4min-6min.

7. The use of the Sn-Er-Beta molecular sieve according to claim 4, characterized in that, The activation process is that the solid substance is calcined at 450℃-550℃ under the condition of argon atmosphere for 6h-8h.

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